[35.04] Planet Embryos in Vortex Wombs

J.A. Barranco, P.S. Marcus (U.C. Berkeley)

One of the enduring puzzles in the formation of planetary
systems is how millimeter-sized dust grains agglomerate to
become kilometer-sized, self gravitating planetesimals, the
"building blocks" of planets. One theory is that the dust
grains settle into the mid-plane of the protoplanetary disk
(thin, cool disk of gas and dust in orbit around a newly
forming protostar) until they reach a critical density that
triggers a gravitational instability to clumping. However,
turbulence within the disk is likely to stir up the dust
grains and prevent them from reaching this critical density.
A competing theory is that dust grains grow by pair-wise
collisions, forming fractal structures. It is unclear,
however, how robust such structures would be to successive
collisions. A new and exciting theory is that vortices in a
protoplanetary disk may capture dust grains at their
centers, "seeding" the formation of planetesimals. We are
investigating the dynamics of 3D vortices in protoplanetary
disks with a parallel spectral code on the Blue Horizon
supercomputer. Some of the lingering questions we address
are: What is the structure of 3D vortices in a
protoplanetary disk? Are they columns that extend vertically
through the disk, through many scale heights of pressure and
density? Or are they more "pancake-like" and confined to the
mid-plane? Are the vortices stable to small perturbations,
such as vertical shear? Are 3D vortices robust and
long-lived coherent structures? Do small vortices merge to
form larger vortices the way vortices on Jupiter do?